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根据室内岩石变形声发射实验结果,计算了声发射序列的地震非均匀度GL值,并以此探讨了岩石破裂失稳的可预测性。在双轴压缩、等速率加载条件下,含障碍体断层、挤压雁列断层和Ⅲ型剪切断层等非连续岩石标本在临近滑动失稳前,声发射活动均出现了显著的均匀—非均匀的状态变化,表现为GL值出现持续大于1的异常变化,GL值异常的位置与破裂成核部位相重合,并与断层走向一致;改变统计窗长、窗内分割数及能级统计下限计算声发射序列的GL值,结果表明,GL值计算结果具有一定的稳定性。综合分析认为,地震非均匀度(GL值)可以较好地刻画岩石失稳前夕因破裂成核导致的声发射活动在时间分布上的状态变化,GL值持续异常是岩石失稳的显著性标志,对预测岩石失稳具有较好的指示意义。 相似文献
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强震前钻孔应变异常变化分析 总被引：1，自引：0，他引：1
利用2007年以来青海省6套YRY-4分量钻孔应变仪数据,对青海地区M≥6.0强震前的前兆异常信息进行研究,并对异常特征进行总结。结果显示:格尔木、门源分量钻孔应变在2008年青海海西6.3级地震前出现了较为可靠的中短期异常,在周边6级以上地震发生前未发现明显临震异常信息。 相似文献
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地震震级频度的古登堡-里克特关系式(简称G-R关系式)一直是许多地震学问题研究的重要前提之一, 然而实际分布常常与这一关系式有一定的偏离。 文中利用已有的对含有凹凸体、 挤压雁列破裂及Ⅲ型剪切破裂等三种类型的岩石实验结果, 对接收到的声发射事件序列分别进行了分段地震震级频度的G-R关系式拟合, 重点考察了每一时间窗内表征实际地震震级频度与这一关系式偏离程度的线性拟合系数r值的变化。 研究结果表明, 含有凹凸体、 挤压雁列破裂的岩石声发射序列在加压－破裂过程中, 分段扫描分别计算得出的r值在标本失稳前出现数字下降的现象, 表明临近岩石失稳, 实际地震震级频度与G-R关系式偏离程度有加大的趋势; 而含Ⅲ型剪切破裂的岩石在标本失稳前, 声发射序列r值数字下降的现象不明显。 部分实际震例也表明, 在一些中强地震前也存在着这种偏离。 研究结果可能对利用区域地震活动资料探求部分类型的中强地震前可能存在的前兆信息具有一定的参考意义。 相似文献
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YRY-4型钻孔应变观测抽水影响分析 总被引：1，自引：1，他引：0
分析泰安基准地震台YRY-4型钻孔应变仪仪器受不同位置抽水的影响,就地下岩石含水变化所产生的地形变干扰,简要分析地下水与地下岩石间的相互作用。这对地震前兆的研究有重要实用意义。 相似文献
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本以两承压岩体相互作用系统作为“弹性回跳”地震模型，用损伤力学的方法研究了系统失稳即地震前位移速率、声发射等前兆规律与岩石破裂过程的关系，用差分法在计算机上求得了地震发生过程中的变形与地声序列曲线，研究发现在某些情况下出现地声相对平静是由于两岩体介质中某一介质体破裂而另一个介质体弹性恢复所致。 相似文献
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Joint FAO/WHO/IOC activities to provide scientific advice on marine biotoxins (research report) 总被引：1，自引：0，他引：1
Toyofuku H 《Marine pollution bulletin》2006,52(12):1735-1745
The Joint FAO/WHO/IOC ad hoc Expert Consultation on Biotoxins in Molluscan Bivalves performed risk assessments for a number of biotoxins present in bivalve molluscs. For performing risk assessments, the Expert Consultation categorized the biotoxins into eight distinct groups based on chemical structure. The Expert Consultation established LOAELs for the azaspiracid (AZA), okadaic acid (OA), saxitoxin (STX), and domoic acid (DA) toxin groups. The derived provisional acute RfDs for the AZA, OA, STX, and DA toxin groups were 0.04 μg/kg bw, 0.33 μg/kg bw, 0.7 μg/kg bw, and 100 μg/kg bw, respectively. For the yessotoxin (YTX) group, a NOAEL was established, based on animal studies. Applying a safety factor of 100, a provisional acute RfD of 50 μg/kg bw was suggested for the YTX group. The Expert Consultation considered that the database for cyclic imines, brevetoxins, and pectenotoxins was insufficient to establish provisional acute RfDs for these three toxin groups. 相似文献
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Sb, As, Cu, and Zn toxicity and contamination have become a growing concern in recent years. Phytoremediation, a plant based and cost effective technology, may be an effective approach in the cleanup of water contaminated by these metals. In this study, the aquatic macrophyte Eleocharis acicularis was used in laboratory and field experiments to assess its capability to accumulate Sb, As, Cu, and Zn, and thereby investigate its potential application in phytoremediation. The results showed that E. acicularis adapted well to water contaminated by these metals. The removal rates of Sb, As, Cu, and Zn in the laboratory experiment were 3.04, 2.75, 0.417, and 1.49 μg/L/day, respectively. The highest concentrations of these metals accumulated in E. acicularis after 10 days of the laboratory experiment were 6.29, 6.44, 20.5, and 73.5 mg/kg dry weight, respectively. Only 8% of As, 12% of Sb, 87% of Cu and 93% of Zn removed from the water were used by E. acicularis. The highest concentrations of Sb, As, Cu, and Zn accumulated in E. acicularis after 10 wk of the field experiment were 76.0, 22.4, 33.9, and 266 mg/kg dry weight, respectively. The results indicate that E. acicularis has the ability to accumulate Sb, As, Cu, and Zn from contaminated water. 相似文献
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De Luca-Abbott SB Richardson BJ McClellan KE Zheng GJ Martin M Lam PK 《Marine pollution bulletin》2005,51(8-12):694-707
Green-lipped mussels, Perna viridis, and Manila clams, Ruditapes philippinarum were sourced from “clean” sites in the Hong Kong region, depurated in a laboratory using uncontaminated filtered seawater for 8 days, and transplanted to a suspected gradient of chemically polluted sites in Hong Kong. After 14- and 28-days of field exposure, several antioxidant parameters including glutathione S transferase (GST), catalase (CAT), glutathione peroxidase (GPx), and glutathione (GSH) were quantified in gill and hepatopancreas tissues. Whole body tissue concentrations of polycyclic aromatic hydrocarbons (PAHs), petroleum hydrocarbons (PHCs), polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCs) were determined in pooled site samples. Chemical analyses indicated that: (a) clams had higher levels of PAHs, PHCs, DDTs and PCBs, whereas mussels had higher hexachlorocyclohexane (HCHs) and there was no difference between species for dieldrin and remaining OCs; (b) Kat O should not be continued as a “clean” reference site for Hong Kong, because of the levels of contaminants measured and (c) PAH concentrations in the current survey were similar to those previously measured. Toxicological conclusions were: (a) antioxidant responses were different between species; (b) CAT and GST have highest utility in clams for field use in Hong Kong, whereas CAT in both gill and hepatopancreas tissue showed most potential in mussels; (c) significant induction of antioxidant responses over day 0 (excluding GPx in both tissues, and GST in mussel hepatic tissue); (d) groups of contaminants do not consistently induce antioxidant responses and (e) organochlorines and PCBs correlated significantly with CAT and GST in clam hepatopancreas and with CAT in mussel gill and hepatic tissue. Multivariate statistical techniques indicated little relationship between the site patterns for antioxidant responses and the contaminant gradients identified in body burden analysis. 相似文献
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Plastic pellets found stranded on beaches are hydrophobic organic materials and thus, they are a favourable medium for persistent organic pollutants to absorb to. In the present study, plastic pellets are used to determine the diffuse pollution of selected Greek beaches. Samples of pellets were taken from these beaches and were analyzed for PCBs, DDTs, HCHs, and PAHs. The observed differences among pellets from various sampling sites are related to the pollution occurring at each site. Plastic pellets collected in Saronikos Gulf beaches demonstrate much higher pollutant loading than the ones collected in a remote island or close to an agricultural area. Based on data collected in this study and the International Pellet Watch program, pollution in Saronikos Gulf, Greece, is comparable to other heavily industrialized places of the world. The present study demonstrates the potential of pellet watch to be utilized as a detailed-scale monitoring tool within a single country. 相似文献
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Ivan Marić Ante Šiljeg Neven Cukrov Vlatko Roland Fran Domazetović 《地球表面变化过程与地形》2020,45(10):2331-2349
Accurate determination of the tufa growth rate (TGR) is required to answer the fundamental geomorphological question of tufa evolution. The TGR has been measured by various direct and indirect methods. One of the most popular direct methods uses modified micro-erosion meter (MEM), which has several drawbacks. Here, we present for the first time a coordinate measuring macro-photogrammetry device (CMD) for monitoring the TGR in a contactless manner. The CMD was applied on 28 limestone plates at 14 locations within the Skradinski buk area, Croatia, and measurements were performed in the laboratory. The TGR was derived from digital tufa high-resolution models (DTHRMs). The accuracy of the device was evaluated using state-of-the-art three-dimensional (3D) scanners and error calculation at checkpoints. Moreover, the precision was evaluated with the split test (n = 5). A total of 74 DTHRMs with a spatial resolution of 0.0236 mm were created. The TGR ranged from 0.327 to 19.302 mm a−1, with an average of 5.771 mm a−1. A higher TGR was observed on the limestone plates near mosses, located in fast and turbulent water rather than in stagnant water. We found that specific micro-environmental factors (e.g. proximity to moss) positively affected tufa growth. Erosion events were observed, as well as the presence of aquatic insect larvae (Simuliidae and Chironomidae), which positively affected tufa growth. The CMD is a precise and accurate device that does not suffer from the drawbacks of the MEM method and has many other advantages. It has a high capability of tufa erosion detection, enables the identification of macroinvertebrates, and multispectral or hyperspectral cameras can be mounted on the device for spectral reflectance analysis of the tufa surface. The CMD can be applied in any study requiring a sub-millimetre data quality and involving the comparison of consecutive 3D models and derivation of various parameters of smaller objects. © 2020 John Wiley & Sons, Ltd. 相似文献
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用增量动力分析方法求解人字形中心支撑钢框架的结构影响系数和位移放大系数(Ⅰ)——方法 总被引：2，自引：1，他引：1
结构影响系数是基于强度的抗震设计中确定设计地震作用的关键,也是基于性态抗震设计理论的基础。位移放大系数则是根据结构的弹性位移估算弹塑性位移的关键参数。本文采用增量动力分析方法求解结构影响系数和位移放大系数,并结合具体算例详细说明了基于增量动力分析求解结构影响系数和位移放大系数的实施步骤。该方法能反映结构的动力特征,并能考虑高阶振型对结构抗震性能的影响。 相似文献
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Projected 21st century climate change on snow conditions over Shasta Dam watershed by means of dynamical downscaling 
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下载免费PDF全文 Snow is an important component of the Earth's climate system and is particularly vulnerable to global warming. It has been suggested that warmer temperatures may cause significant declines in snow water content and snow cover duration. In this study, snowfall and snowmelt were projected by means of a regional climate model that was coupled to a physically based snow model over Shasta Dam watershed to assess changes in snow water content and snow cover duration during the 21st century. This physically based snow model requires both physical data and future climate projections. These physical data include topography, soils, vegetation, and land use/land cover, which were collected from associated organizations. The future climate projections were dynamically downscaled by means of the regional climate model under 4 emission scenarios simulated by 2 general circulation models (fifth‐generation of the ECHAM general circulation model and the third‐generation atmospheric general circulation model). The downscaled future projections were bias corrected before projecting snowfall and snowmelt processes over Shasta Dam watershed during 2010–2099. This study's results agree with those of previous studies that projected snow water equivalent is decreasing by 50–80% whereas the fraction of precipitation falling as snowfall is decreasing by 15% to 20%. The obtained projection results show that future snow water content will change in both time and space. Furthermore, the results confirm that physical data such as topography, land cover, and atmospheric–hydrologic data are instrumental in the studies on the impact of climate change on the water resources of a region. 相似文献
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In this study, the distribution and partition of polybrominateddiphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) in water from the Pearl River Estuary were investigated. A seasonal dependence for dissolved and particle phase PCB and PBDE levels was observed. A high dissolved phase level occurred in the dry season. The positive correlation between POC content in the particles and phase distribution coefficients (Kp) suggested that POC may play an important role in determining the partition of PBDEs and PCBs. A linear correlation between the observed log KOC and log KOW for PBDEs and PCBs was found with slopes less than one. The observed log KOC values were lower than the predicted log KOC values for PBDEs (except for BDE28). The log KOC values were higher than the predicted values for PCBs. A combination of sorption to colloids (10-98% for PBDEs and less than 25% for PCBs) and adsorption to BC was responsible for this observation. 相似文献
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Data-based modelling approach for variable density flow and solute transport simulation in a coastal aquifer 总被引：1，自引：1，他引：0
Data-based models, namely artificial neural network (ANN), support vector machine (SVM), genetic programming (GP) and extreme learning machine (ELM), were developed to approximate three-dimensional, density-dependent flow and transport processes in a coastal aquifer. A simulation model, SEAWAT, was used to generate data required for the training and testing of the data-based models. Statistical analysis of the simulation results obtained by the four models show that the data-based models could simulate the complex salt water intrusion process successfully. The selected models were also compared based on their computational ability, and the results show that the ELM is the fastest technique, taking just 0.5 s to simulate the dataset; however, the SVM is the most accurate, with a Nash-Sutcliffe efficiency (NSE) ≥ 0.95 and correlation coefficient R ≥ 0.92 for all the wells. The root mean square error (RMSE) for the SVM is also significantly less, ranging from 12.28 to 77.61 mg/L. 相似文献
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ABSTRACT Karst aquifers and springs are important with respect to their potential for supplying drinking water in regions suffering from water scarcity in Iran. Accordingly, it is essential to determine the recharge potential of the catchment and the regions with higher obtainability potential. This study provides a road map for the Sheshpeer catchment in southern Iran. A recharge potential (RP) map was produced from which a recharge index (RI) was computed for several selected springs in the catchment. Furthermore, the unit discharge (q) – defined as the average annual discharge for a given catchment area and unit rainfall depth for each spring – was calculated. The plot of q versus RI for the springs showed a linear positive relationship between the two variables (R 2 = 0.9). Applying the trend equation of this plot to the whole Sheshpeer karstic catchment reveals that its long-term recharge coefficient is 0.74. 相似文献